Strong Magneto-Optical Response of Nonmagnetic Organic Materials Coupled to Plasmonic Nanostructures

Abstract

Plasmonic nanoparticles (PNPs) can significantly modify the optical properties of nearby organic molecules and thus present an attractive opportunity for sensing applications. However, the utilization of PNPs in conventional absorption, fluorescence, or Raman spectroscopy techniques is often ineffective due to strong absorption background and light scattering, particularly in the case of turbid solutions, cell suspensions, and biological tissues. Here we show that nonmagnetic organic molecules may exhibit magneto-optical response due to binding to a PNP. Specifically, we detect strong magnetic circular dichroism signal from supramolecular J-aggregates, a representative organic dye, upon binding to silver-coated gold nanorods. We explain this effect by strong coupling between the J-aggregate exciton and the nanoparticle plasmon, leading to the formation of a hybrid state in which the exciton effectively acquires magnetic properties from the plasmon. Our findings are fully corroborated by theoretical modeling and constitute a novel magnetic method for chemo- and biosensing, which (upon adequate PNP functionalization) is intrinsically insensitive to the organic background and thus offers a significant advantage over conventional spectroscopy techniques.

Magnetic Circular Dichroism in Nanomaterials: New Opportunity in Understanding and Modulation of Excitonic and Plasmonic Resonances

“…The new MCD signals were shifted from the extinction peaks of noninteracting molecule and core-shell Au@ Ag nanorods (Figure 10a-c). [120] Theoretical model indicated that when the longitudinal mode of Au@Ag nanorods was resonant with the J-band of dye J-aggregates, two plexciton states (upper resonance-UR and lower resonance-LR) were induced due to the intense coupling interaction between the nanorods plasmon and the J-aggregates exciton. Both plexcitons possessed the features combining excitons and plasmon (Figure 10d).…”

Encapsulating Au‐Fe3O4 Nanodots into AIE‐active Supramolecular Assemblies: Ambient Visible‐light Harvesting “Dip‐Strip” Photocatalyst for C−C/C−N Bond Formation Reactions

“…Moreover,m ost of the reported synthetic protocolsf or the preparation of Au-Fe 3 O 4 nanohybrid materials requireh arsh reaction conditions such as high temperature, additives,r educing agentsa nd prolonged reaction time which decreases the environment/economica dvantages of the strategy. [4] In view of the applications of magneto-plasmonicsi ndiverse fields such as optics, imaging, sensing, solar cells, biomedicals and catalysis, [5] it is highly desirable to develop a rapid and convenientp rotocol for their preparation.…”

Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities: an overview on properties and applications [Invited]

“…In this framework, and thank to the development of simple fabrication routes for the metal nanoparticles (e.g., by colloidal chemistry based on reduction of metal salts [51]) and nanoparticle arrays (e.g., by nanosphere colloidal lithography [52][53][54][55][56]), LSPs have been found to be suitable for a wide range of applications, including subwavelength imaging and superlensing [57 -61], nanolasing [62][63][64], light trapping and concentrators [65][66][67], plasmon-enhanced optical tweezers [68][69][70] supersensitive plasmonic metamaterials sensors [71][72][73][74], improved photovoltaic devices [75] active optical elements [76,77] etc. In this framework, magnetism have emerged as a valuable route to add an extra degree of freedom to plasmonics, since it allows to actively induce significant changes in the optical response of meta-atoms either entirely [78][79][80][81][82][83][84][85]or partially [86][87][88][89][90][91] made of magnetic materials and supporting LSPs (for a detailed overview we refer the reader to the reviews by Maksymov [ 92], and Pineider and Sangregorio [ 93]). More in detail, magnetic materials possess what is called a magneto-optical (MO) activity, arising from spin-orbit coupling of electrons, resulting in a weak magnetic-field i...…”